Impeller for blowers



June 2, 1942.

J. FULLEMANN IMPELLER FOR BLOWERS Filed Dec. 1'7, 1940 2 Sheets-Sheet 1 J. FULLEMANN IMPELLER FOR BLOWERS June 2-, 1942.

2 Sheets-Sheet 2 Filed Dec. 17, 1940 main Jun 2,.l942

UNITED STATES' PATENT- OFFlCE f azssase' s 7 IMPEILER FOB BLOWEBS Johann Fiillemann, Winterthur, Switzerland, as- .slgnor to Alfred J. Biichl, Winterthur, Switzerland' 3 Application December 11', aiofseriai Nb. z'lassz loam (Cl. 230430 This invention relates to improvements in impellers for rotary gas blowers and particularly to. impellers of the closed" type, that is, impellers. in which vanes which extend in a generally radial direction are closed at their sides by discs, so that passages are formed by the'vanes and discs which are open only at their inner and" outer ends.

An object of this. invention is'to provide an impeller ofthe closed type adapted to be formed with the vanes and side-face discs in one single piece, for instance by a casting operation.

A further object of this invention is to provide vanes having fluid foil shape in cross section for the sake of efilciency in operation and having thick middle portions for facilitating and enabling the flow of molten metal to pass through the corresponding spaces in the mold in the easting operation without solidifying prematurely and thereby to reach all parts of the mold and form perfect castings.

A still further object of this invention is to provide impellers of this kind with vanes which are outwardly straight or, if curved at all, of such slight curvature that the side surfaces, due to their fluid foil shape, will-be straight or slightly convex or will. have no strongly concave parts, considered in the outward direction of extent of the vanes; whereby the finishing, smoothing or polishing of said surfaces can be performed more expeditiously by hand or even by machine than if the said surfaces were strongly concave. This feature is particularly desirable in an impeller cast-in'one piece because it is very difiicult to smooth the vane surfaces, which operation could be performed rather simply if one of the side ringswere formed separately and attached afterward.

ed to operate at high speeds without the'genercasting operation and having surfaces which face Another object of this invention is to provide a cast impeller forgas blowers which is formed in the greater part of light-weight metal adaptation of excessively powerful centrifugal forces, and reinforced at certain critical points, preferably located relatively close to the axis of rotation by bands of particularly strong metal resistant to the centrifugal forces, said reinforcements be ing made integral with the'other material in the inwardly toward the axis of rotation and are engaged by the light-weight metal. The reinforcements, usually being of heavier weight material than the rest of the impeller, are located as close impeller taken on the line 11-11 of Fig. 1;

Fig. 3 is a transverse sectional view similar to Fig.1 of an impeller having vanes of different cross-sectional shape, the other parts of the Still another object of this invention is to provide a gas impeller wlthvanes having suflicient a thickness at the center portion to ensure reliable casting and at the same time having forward, that is,- inner, edges-which are thin and properly rounded to give good aerodynamic efficiency and to have a good effect for noise '(whistling) re-,

of rotation of the impeller, whereby improvement in pressure relative to the circumferential speed of 'the'impeller is attained over wardly curved vanes. I

the ordinary backblower being omitted; I

I Fig. 4 is a transverse sectional view similar to Fig. 3 of an impeller having vanes of still different cross-sectional shape; and

Fig; 5 Ban axial sectional view similar to Fig.

2 of part of an impeller showing a different form of reinforcement.

' :sides of the impeller, and a spiral, volute-shaped gas conduit 6 of progressively enlarging size toward an outlet I.

Within the blower casing I (Fig. 1) is mounted a rotary "impeller III mounted ondriving shaft I I.

The impeller isof the type generally known as closed. By this -is meant that both sides of the gas passagesformed between the impeller vanes are closed by disc-like plates I2 and I3 respectively. The plate l2 has a hub portion l5 into or through which driving shaft ll extends, and plate l3 has a large central opening l6 which serves as an entrance for the gas, plate l3 being therefore of ring shape. It is also to be observed that the inner periphery of.ring-shaped disc I3 is axially thickened so as to extend more or less abruptly beyond its side walls, and this enlarged flange-like portion I8 is provided with a reinforcing band l9 of a relatively heavy metal of high tensile strength and modulus of elasticity, for instance. steel, cast in the light-weight metal of the flange to assist in resisting deformation of the impeller under the influence of the strong forces created by centrifugal action when the impeller rotates at high speed. The impeller may be cast of a light-weight aluminum alloy for minimizing the centrifugal force and weight involved, the reinforcing being initially placed in position in the mold before pouring.

Between the two discs l2 and I3 extend a plurality of flat vanes 24 cast integrally with said discs. The shape and arrangement of these vanes are among the principal features of the present improvements. As shown in Figs. 1, 3 and 5, these vanes 24, 24a and 24b are of fluid foil cross section considered on a section plane extending transversely to the axis of rotation of the impeller. In the embodiment shown in Fig. 1, the central axes of the vanes are straight and the vanes are of double fluid foil shape, that is, both surfaces are curved in conformity of fluid foils. The principal characteristics of this shape are that the inner edges are comparatively thin and are smoothly rounded off, the central widths are comparatively great while the outer edges are relatively thin, preferably even thinner than the inner edges, and the intermediate surfaces gradually pass over into one another without abrupt changes of direction. The purposes of the fluid foil cross section and the roundness of the inner and outer edges are to improve the aerodynamic efficiency of the impeller, reduce the resistance of the air flow, and minimize the whistling noise incident to operation of such apparatus at high rotary speeds.

The vanes are preferably arranged between the discs at angles inclined forwardly with respect to the respective radial planes, that is, the vanes lie in planes which would extend tangent to a cylinder coaxial and concentric with the axis of revolution. This arrangement materially improves the aerodynamic efficiency in operation. The relatively thick central sections of the vanes enable the impeller to be cast with the two discs and vanes all in one piece, the large flow area of the thick central portions of the vanes facilitating flow of the molten metal to all parts of the vanes and between the discs without the danger of imperfections occurring from premature chilling and solidifying of the metal.

The cross-sectional shape of the vanes may be altered to some extent, for instance, as indicated in Fig. 3, in which one side of the vanes is substantially fiat while the other side is relatively more strongly convex than in Fig. 1. However, the important features of the shape, rounded inner and outer edges, relatively thick central portions providing fluid foil section, and the avoidance of strong concavity at any point are maintained. This latter feature, avoidance of strong concavity, enables the surfaces of the vanes to be smoothed and possibly polished by simple hand operations. whereas if strongly concave surfaces were formed, considerable difficulty would be enaasazee countered in finishing the concave surfaces either by hand or machine, and therefore would render the production of the impellers by integral casting a very diflicult or impractical matter.

A further embodiment of the shape of the vanes is shown in Fig. 4 in which the vanes 2412 are formed as double fluid foils but about curved surfaces whereby the forward surfaces are substantially flat Or only slightly concave while the after surfaces are of stronger convexity. In this case, also, the important features of the shape of the vanes are adhered to, that is, the thin,

rounded inner and outer edges, the relatively thick central portions, the fluid foil shape, and the avoidance of strongly concave surfaces. The curvature of the curved surfaces about which the vanes are formed is preferably such that their outer edge portions extend approximately or exactly parallel or coincident with the respective radii R of the impeller axis.

Fig. 5 illustrates another embodiment of reinforcement 26 for the flange I8a of disc I3a, and also in this embodiment the hub l5a of disc In is provided with a similar reinforcement ring or coil 21. The reinforcement members 26 and 21 may be round bands of steel entirely embedded in the light weight metal by casting or may be helical springs.

By forming the impeller according to the present invention, it is an entirely practical matter to cast it in one casting operation, particularly by reason of the large flow areas of the central portions of the vanes, and to finish or polish the vanes and other parts by simple operations without such difficulties as would arise if strongly concave surfaces were formed on the vanes, while at the same time, the thickness of the vanes does not impair the aerodynamic efficiency of the blower; but, on the contrary, the fluid foil section and forward pitch of the vanes provide efficiency unsurpassed even by very thin vanes which are entirely impractical for casting, and, furthermore. the shape of the vanes is such as to minimize the whistling noise incident to highspeed operation.

I claim:

1. A rotary impeller of the closed type for centrifugal gas blowers comprising a plurality of impeller vanes extending generally outwardly from the axis of rotation of the impeller and angularly spaced apart from each other, a pair of discs closing the sides of the spaces between the vanes so that only the inner and outer ends of the gas passages provided by said spaces are open, said discs and vanes being formed of a single piece of metal, the material of said vanes and discs bein light-weight metal to reduce centrifugal force, one of said discs having a relatively wide hub portion, and a reinforcement band extending around said hub located entirely within the metal of said hub portion and integrally united therewith, said band being of a heavier, stronger metal than the rest of the disc.

2. A rotary impeller of the closed type for centrifugal gas blowers comprising a plurality of impeller vanes extending generally outwardly from the axis of rotation of the impeller and angularly spaced apart from each other, a pair of discs closing the sides of the spaces between the vanes so that only the izmer and outer ends of the gas passages provided by said spaces are open, the material of said vanes and discs being light-weight metal to reduce centrifugal force, one of said discs having a relatively wide hub portion, a substantially ring-shaped reinforcemerit band extending around said hub located entirely within the metal or said hub portion,

said band being of a heavier, stronger metal than the rest of the disc, and the other of said discs the vanes so that only the inner and outer ends of the gas passages provided by said spaces are open, one of said discs having a comparatively thick central hub portion, a spring'steel coil integrally embedded in said hub portion entirely within the metal of said hub, the other disc having a thickened inner edge portion, and a ringlike member of heavy strong metal entirely embedded in and integrally united with .said edge portion and extending entirely around said inner edge.

p 4. A rotary impeller of the closed type for centriiugal gas blowers comprising a plurality of impeller vanes extending generally outwardly from the axis of rotation of the impeller and angularly spaced apart from each other, a pair of discs closing the sides of the. spaces between the vanes so that only the inner and outer ends of the gas passages provided by said spaces are open, said discs and vanes being formed of a single piece of metal, said vanes being substantially straight in the inward-outward direction. so as to be free of concave surfaces, the materialof said vanes and discs being light-weight metal to reduce centrifugal force, one of said discs having a relatively wide hub portion, and a reinforcement band extending around said hub located entirely within the metal of said hub portion and integrally united therewith, said band being of a heavier, stronger metal than the rest of the disc.

JOHANN F'UHEMANN. 

